In Syria, humanitarian aid workers represent a lifeline to people in towns torn by conflict. They bring everything from food and medicine to school supplies, and they're paying a price for that. Even as diplomats in Geneva try to salvage a cease-fire to get aid to civilians, the Syrian regime and other forces have arrested and even killed these workers. NPR's Michele Kelemen has their story.

MICHELE KELEMEN, BYLINE: Back in 2012, Sandra Bitar spent a harrowing month in the custody of Syria's secret police.

SANDRA BITAR: Because I sent baby milk to Baba Amr in Homs.

KELEMEN: Her story is actually not unusual. Aid workers have been arrested, even killed for doing basic charity work in Syria, especially when they try to smuggle goods into besieged towns. When Bitar asked her interrogators what she did wrong, she says this is how they answered.

BITAR: They said that I supporting the terrorist families. I said, but I'm sending food for babies. It's baby milk. They said, these children is a bad seed and we have to kill them all, from the father to the son.

KELEMEN: Bitar was here in Washington today for a conference organized by the aid group CARE. In an interview, she spoke about her time in prison, where she says she saw one colleague tortured in front of her.

BITAR: This place where they detain people, it's not place for a human being. You keep hearing screaming all night from people who are tortured.

KELEMEN: Bitar was released after 35 days and tried to continue her work providing psychological care to children in Syria. But when, as she put it, a double agent tipped her off that she was about to be arrested again she fled, and now lives in Turkey, where she runs an aid group called Emissa. Her husband and co-worker, Farouq Habib, says three of their colleagues back in Syria have been killed and several have been arrested. He, too, spent a couple of months in jail, and is appealing to the U.N. to help.

FAROUQ HABIB: In the beginning, we were asking for protection for civilians all over Syria. Now at least we ask for protection for humanitarian workers.

KELEMEN: Habib says he made that case to the U.N. in Geneva recently, but doesn't sound very optimistic.

HABIB: The U.N. is helpless on this. They just wait for the Americans and the Russians to agree on something.

KELEMEN: Secretary of State John Kerry has been working with his Russian counterpart to try to salvage a cease-fire in Syria. He's also been encouraging Russia to use its influence with Bashar al-Assad's regime to make sure aid workers have the access they need to help civilians.

A top adviser to the U.N. on humanitarian issues in Syria, Jan Egeland, says he doesn't know how many aid workers have been jailed in Syria. He believes there are many, and they face dangers from the government and from the rebels.

JAN EGELAND: Those who try to smuggle in relief to besieged areas - either besieged by the government in most cases, but also armed opposition groups - are doing that at great risk. These are true heroes.

KELEMEN: The U.N. has to negotiate with the Syrian government to get convoys to besieged areas. And access is still too limited, Egeland says, especially when it comes to medical supplies.

EGELAND: The Syrian government is taking away surgical kits, trauma kits, even basic health kits, scissors out of midwives' suitcases. It is incredible.

KELEMEN: The Syrian aid worker Sandra Bitar says such violations of humanitarian law are shameful, and she doesn't think the U.N. or the U.S. are doing enough to stop this. Michele Kelemen, NPR News, the State Department. Transcript provided by NPR, Copyright NPR.